This pilot project is an investigator-initiated, 12-month, randomized, crossover trial to determine if use of the i-STAT device reduces acute health care visits for fluid and electrolyte imbalance and health care costs of these patients. We plan to recruit 8-10 patients with diabetes insipidus and either limited access to free water (infants or neurologically impaired) or adipsia/hypodipsia. Patients will be followed for 12 month blocks alternating with and without the i-STAT device.